// GenericsNote: Converted.
/*
 *  Copyright 2003-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.jivesoftware.smack.util.collections;

import java.util.Map;

/**
 * Abstract Pair class to assist with creating correct Map Entry
 * implementations.
 * 
 * @author James Strachan
 * @author Michael A. Smith
 * @author Neil O'Toole
 * @author Matt Hall, John Watkinson, Stephen Colebourne
 * @version $Revision: 1.1 $ $Date: 2005/10/11 17:05:32 $
 * @since Commons Collections 3.0
 */
public abstract class AbstractMapEntry<K, V> extends AbstractKeyValue<K, V>
		implements Map.Entry<K, V> {

	/**
	 * Constructs a new entry with the given key and given value.
	 * 
	 * @param key
	 *            the key for the entry, may be null
	 * @param value
	 *            the value for the entry, may be null
	 */
	protected AbstractMapEntry(K key, V value) {
		super(key, value);
	}

	// Map.Entry interface
	// -------------------------------------------------------------------------
	/**
	 * Sets the value stored in this Map Entry.
	 * <p/>
	 * This Map Entry is not connected to a Map, so only the local data is
	 * changed.
	 * 
	 * @param value
	 *            the new value
	 * @return the previous value
	 */
	public V setValue(V value) {
		V answer = this.value;
		this.value = value;
		return answer;
	}

	/**
	 * Compares this Map Entry with another Map Entry.
	 * <p/>
	 * Implemented per API documentation of
	 * {@link java.util.Map.Entry#equals(Object)}
	 * 
	 * @param obj
	 *            the object to compare to
	 * @return true if equal key and value
	 */
	public boolean equals(Object obj) {
		if (obj == this) {
			return true;
		}
		if (obj instanceof Map.Entry == false) {
			return false;
		}
		Map.Entry other = (Map.Entry) obj;
		return (getKey() == null ? other.getKey() == null : getKey().equals(
				other.getKey()))
				&& (getValue() == null ? other.getValue() == null : getValue()
						.equals(other.getValue()));
	}

	/**
	 * Gets a hashCode compatible with the equals method.
	 * <p/>
	 * Implemented per API documentation of
	 * {@link java.util.Map.Entry#hashCode()}
	 * 
	 * @return a suitable hash code
	 */
	public int hashCode() {
		return (getKey() == null ? 0 : getKey().hashCode())
				^ (getValue() == null ? 0 : getValue().hashCode());
	}

}
